Forecasting the response of Great Lakes sea lamprey (Petromyzon marinus) to barrier removals

A key uncertainty surrounding barrier removals in the Great Lakes is the response of invasive sea lamprey (Petromyzon marinus) populations to realized increases in available habitat for adfluvial species. We addressed this uncertainty by applying a management strategy evaluation model, originally developed to inform sea lamprey management in the Great Lakes, to forecast the effects of barrier removal on Lake Michigan sea lamprey abundances. We used this model to characterize the response to systematically increasing habitat availability and a specific proposed barrier removal. Our results suggest the removals allow novel production from newly opened habitat and, assuming a fixed budget for sea lamprey control, decrease the overall effectiveness of control, leading to disproportionate increases in abundance. The case study demonstrated that evaluating population effects only at the scale of watersheds directly affected by barrier removals would substantially underestimate effects at the scale of Lake Michigan. Similar population responses are possible when evaluating the effects on desired species. Our findings highlight the importance of considering trade-offs for barrier removals and selecting the appropriate scale for forecasting.